The objective of this research proposal is to increase our knowledge of the antigens that are present on the cell surface of Streptococcus mutans since this knowledge is an essential basis for immunoprophylactic studies related to dental caries. This will be done by characterizing the rhamnose-containing polymers (RCP) that are present in the cell walls of S. mutans serotypes a, d, and g strains. The RCPs will be extracted from cell walls using hot acidic conditions, chromatographically purified, and chemically characterized. The immunogenicity of the RCPs will be examined using a passive hemagglutination assay to screen antisera to whole cells and RCP-wall preparations for antibodies that are specific for the RCP. Both reactivity among the RCPs and between the RCPs and the serotype-specific polysaccharides (SSP) of S. mutans. Agar gel diffusion, tandem cross-immunoelectrophoresis, and the passive hemagglutination assays will be used in these studies. The specificity of the antigenic determinants on the RCP will be examined by inhibition studies utilizing di- and tri-saccharides isolated and characterized from partial acid hydrolysis of the RCP. Immunoelectron microscopic studies will be used to verify the localization of the RCP and the SSP in the microcapsular or cell wall material of S. mutans. Semi-quantitative changes in these surface antigens in response to differences in growth media will also be observed.